The prostates of 41 foetuses and neonates have been assayed for testosterone, 5 alpha-dihydrotestosterone (DHT), oestradiol and oestriol and the presence of these hormones has been demonstrated in all cases. Oestriol was found to be present in the highest concentration. A highly significant correlation was found between testosterone and DHT as well as between DHT and oestradiol. The correlation between oestriol and oestradiol was also significant. It has been pointed out that the presence of these hormones is essential for the growth and development of the prostate gland.